Turbochargers used with engines, such as internal combustion engines, generally deliver compressed air to an engine intake. The compressed air allows more fuel to be combusted and, thus, boosts an engine's horsepower without significantly increasing the size of the engine. As such, turbochargers allow for smaller engines to produce similar horsepower as larger, alternative, non-turbocharged engines. Furthermore, using a turbocharger reduces fuel usage by providing more complete combustion of the fuel delivered to the engine.
In general, a turbocharger, typically, includes a turbine connected to an exhaust of the engine, a compressor connected to the engine's air intake, a bearing housing disposed between the turbine and compressor, and a shaft housed by the bearing housing and connecting the turbine and compressor. The turbine is driven by an inflow of exhaust gas supplied by the engine. The shaft, rotatably supported by the bearing housing, connects the rotating turbine to the compressor, such that rotation of the turbine causes rotation of the compressor. As the compressor rotates, it increases the air mass flow rate, airflow density, and/or air pressure delivered to cylinders of the engine, via the engine's air intake.
While the rotation speed of the turbine and compressor depend upon sizes of wheels of both the turbine and compressor, in general, the turbine wheel and, in turn, the shaft of a turbocharger rotate at very fast rates. For example, a turbocharger turbine wheel and shaft used in conjunction with an internal combustion engine can reach circumferential speeds of over 500 meters per second. Furthermore, as said turbochargers are often used in engines, they are, therefore, exposed to high temperature environments caused by combustion within the engine. Heat caused by both the engine environment and friction from the high rotational speeds may cause undesired heat along the shaft and, more generally, within the bearing housing. As such, to combat excess heat, combat excess friction, and/or to properly cool the bearing housing, conventional turbochargers, generally, include oil lubrication and cooling systems to properly lubricate and cool the shaft and bearing housing.
In such an oil-lubricated turbocharger, oil is pumped to the shaft to provide necessary lubrication and cooling. However, oil must be continuously pumped into and removed from the bearing housing, as excessive oil build-up within the bearing housing may cause leakage through seals into one or both of the turbine and compressor. Further, if oil remains in the bearing housing for too long of a time, it can degrade due to overheating and may, in some circumstances, form coke. In general, oil may flow away from the bearing housing due to gravity, rather than by using a pump. For example, in an automotive turbocharger, oil may exit the bearing housing and flow to an engine oil sump, wherein the oil is cooled and then recirculated to lubricate one or both of the engine and the turbocharger.
To help improve oil flow within the bearing housing of a turbocharger, various systems and methods are implemented, such as those described in U.S. Patent Application Publication No. 2013/0142679 (“Exhaust-Gas Turbocharger”). In the '679 publication, bearing bushes of the housing may include an oil collecting chamber arranged to delimit a gap and prevent oil from entering a turbine section of the turbocharger. While such chambers certainly may be useful in oil flow, they do not account for oil swirling in the drain and oil build up from improper flow. Therefore, a turbocharger bearing housing, which includes an oil core that improves oil flow to a drain, is desired.